It is known to prepare bisphenols, e.g. bisphenol A, by continuously reacting in a reaction zone at least 2 moles of a phenol and a carbonyl compound in the presence of an acidic catalyst, such as hydrochloric acid, sulfuric acid or a cation-exchange resin. The reaction effluent, in addition to unreacted starting materials and the desired bisphenol product typically contains reaction by-products and color bodies. Exemplary processes are described e.g., in the U.S. Pat. Nos. 1,977,627, 2,730,552, 3,049,568, 4,053,522, 4,191,813, 4,308,404 and 4,308,405 incorporated herein by reference. Usually the desired bisphenol product is separated as an adduct with phenol, and the mother liquor which contains the condensation by-products is recycled to the principal reaction zone, or to a second reaction zone, for at least partial conversion to the desired bisphenol, as described e.g., in U.S. Pat. Nos. 3,049,569 and 3,221,061 incorporated herein by reference.
The bisphenol products of such processes are themselves starting materials in the production of materials such as epoxy resins, polycarbonates, polysulfones, and antioxidents. With the advance of technology employing these materials it has become increasingly important that the bisphenols be color-free, i.e., contain few, if any color bodies. Cation exchange resins have proven useful adsorbents for adsorbing color bodies from the mother liquor. However, such resin adsorbents have only limited adsorption capacity, and it is desirable to be able to effectively and efficiently wash the color bodies from the cation ion exchange resins to restore their utility. Regeneration procedures employing acidified phenol/water wash as described in U.S. Pat. No. 4,051,079 or employing a mixed phenol/water wash as described in U.S. Pat. No. 4,107,218 have been only partially effective. An improved process has now been found wherein the color bodies may be effectively removed by washing with an aqueous solution of certain phenates.